Multispherical subsea enclosures

ABSTRACT

A watertight enclosure for the underwater confinement of a device includes a set of ellipsoidal modules juxtaposed in a watertight manner and internally delimiting at least one volume receiving the device. It has been found that producing a watertight enclosure by means of juxtaposed ellipsoidal modules enables a total weight saving of the order of one third compared to a cylindrical envelope.

BACKGROUND OF THE INVENTION

Embodiments of the present invention is generally concerned withwatertight enclosures for the underwater confinement of various types ofdevice.

Some types of industry, for example in the field of gas or petroleumexploitation, necessitate the immersion at very great depths ofelectrical or electromechanical devices.

Such industries for example necessitate the immersion at great depths ofelectrosubmersible pumps (ESP) together with their electrical powersupply system.

In this type of application the depths reached can reach or even exceed3,000 metres.

The immersed devices are generally placed in a watertight envelope inorder to protect their internal components from seawater.

To protect the devices against pressure, two principal designs exist forthe production of a confinement enclosure.

In accordance with a first type of design, the enclosure is filled witha liquid that is not electrically conductive, generally dielectric oil,in pressure balance with the sea. The equipment placed in the enclosureis then subjected to the immersion pressure and must furthermore becompatible with the oil. As the pressure is balanced, the walls of theenclosure are not subjected to stress linked to the pressure andtherefore do not need to be made with a thickness increasing with theimmersion depth.

In accordance with the second type of design, the enclosure is filledwith a gas (air, nitrogen, . . . ) at low pressure, generally close toatmospheric pressure. The walls of the enclosure are sized to resist theimmersion pressure. The equipment is then installed under conditionssimilar to those of industrial use.

Embodiments of the present invention relates to the second type ofenclosure, known as an “atmospheric pressure” enclosure.

Clearly, the thickness of the enclosure must increase as the immersiondepth increases, as a function of the pressure it has to withstand.

The watertight enclosures for the underwater confinement of a device aregenerally based on a cylindrical envelope comprising two end domes.

For example, for an immersion depth of approximately 3,000 metres thethickness of the cylindrical envelope can reach 80 mm with the resultthat, for an envelope having a length of 7 m and an inside diameter of 2m, the total mass of the envelope including the equipment that itcontains can reach or even exceed 40 tons, which necessitates powerfullifting means.

There also exist spherical envelopes which, because of their shape, makeit possible to reduce considerably the thickness of the materialentering into the constitution of the envelope.

Although the production of a spherical envelope makes it possible tosave weight, it has been found that this type of design has majordisadvantages in terms of integration in that, compared to a cylinder, asphere increases the footprint and therefore leads to a larger andheavier supporting structure.

BRIEF DESCRIPTION OF THE INVENTION

Given the foregoing, there is proposed a watertight enclosure that isrelatively easy to manufacture but of lower weight compared tocylindrical envelopes.

In accordance with a first aspect of the invention, there is proposed awatertight enclosure for the underwater confinement of a device,including a set of ellipsoidal modules juxtaposed in a watertight mannerand internally delimiting at least one volume receiving the device.

It has been found that producing a watertight enclosure by means ofjuxtaposed ellipsoidal modules enables a total weight saving of theorder of one third compared to a cylindrical envelope.

In one embodiment, the watertight enclosure includes a removable endmodule of hemispherical dome shape connected to said set of modules by awatertight flange.

In accordance with an aspect, the ellipsoidal modules are connected inpairs by cylindrical connectors.

These cylindrical connectors may have a thickness greater than that ofthe ellipsoidal modules.

In one embodiment, the cylindrical connectors are equipped withstiffener elements.

For example, these stiffeners are formed by a localized enlargement ofthe cylindrical connectors.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the invention will becomeapparent on reading the following description, given by way ofnonlimiting example only and with reference to the appended figures, inwhich:

FIG. 1 is a profile view of a watertight enclosure; and

FIG. 2 is a partial sectional view of the enclosure from FIG. 1.

DETAILED DESCRIPTION

Refer first to FIG. 1, which shows the general architecture of awatertight enclosure, designated by the general reference number 1, forthe underwater confinement of a device.

In this figure, the watertight enclosure is represented in a positionassumed vertical.

In the application that is envisaged, this enclosure is intended toprotect one or more immersed electrical or electromechanical devices,such as a variable speed drive, a low-voltage or high-voltagedistribution unit, a power supply system with back-up, . . . Of course,it is not outside the scope of the invention for it to be intended toreceive other types of device.

As seen in FIG. 1, the enclosure 1 includes a set of ellipsoidal modules2, 3 and 4, here 3 in number, disposed in line with one another andconnected in pairs by cylindrical portions 5, 6 and 7.

At each end the envelope includes a dome 8 of truncated sphere shapeconnected in watertight manner to one of the ellipsoidal modules and, atthe opposite end, a hemispherical dome 9 connected to the other endellipsoidal module 2.

The ellipsoidal modules and the end domes together delimit an internalvolume filled with nitrogen at atmospheric pressure and intended toreceive the device to be immersed. Of course, the number of modules isnot limiting on the invention and may be chosen as a function of theoverall size of the device.

In reality, each of the ellipsoidal modules has a flattened sphere shapeand is more particularly formed by the spherical zone of a flattenedsphere contained between two parallel planes such as P1 and P2.

Because of the production of the various modules with a partiallyspherical shape, the modules and the end domes 8 and 9 have a smallerthickness compared to the thickness of a cylindrical envelope necessaryto withstand the immersion pressure. For example, for an immersionpressure that can reach 3,000 metres, the thickness of the sphericalwall is therefore of the order of 50 mm.

Where the cylindrical connectors 5 and 6 are concerned, these have anincreased thickness determined to provide the stiffness of the whole,for example of the order of 150 mm.

It will be noted that the diameter of the hemispherical dome 9 is lessthan the inside diameter of the cylindrical connectors 5, 6 and 7 andchosen so as to be greater than the greatest transverse dimension of thedevice so that after introduction of a device via the opening of the endellipsoidal module 2 no problem can occur with insertion of the deviceinto the rest of the enclosure.

The hemispherical dome 9 therefore in reality constitutes a removableelement and is fixed to the hemispherical module 2 by means of a flange10.

Finally it is seen in FIG. 1 that the cylindrical connectors 5, 6 and 7may be provided with a stiffener, such as 11, produced in the form of alocalised thickening of material. Such a stiffener 11 remains optional,however, and has been shown for only one of the cylindrical connectors.

Clearly, the watertight enclosure that has just been described, whichuses a set of juxtaposed ellipsoidal modules, enables the thickness ofthe enclosure to be considerably reduced at the location of theellipsoidal modules. The weight saving can therefore be as much as onethird compared to cylindrical enclosures.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal languages of the claims.

1. A watertight enclosure for the underwater confinement of a device,comprising: a set of ellipsoidal modules juxtaposed in a watertightmanner and internally delimiting at least one volume receiving thedevice.
 2. The watertight enclosure according to claim 1, including aremovable end module of hemispherical dome shape connected to said setof modules by a watertight flange.
 3. The watertight enclosure accordingto claim 1, wherein the ellipsoidal modules are connected in pairs bycylindrical connectors.
 4. The watertight enclosure according to claim3, wherein the cylindrical connectors have a thickness greater than thatof the ellipsoidal modules.
 5. The watertight enclosure according toclaim 3, wherein the cylindrical connectors are equipped with stiffenerelements.
 6. The watertight enclosure according to claim 5, wherein thestiffeners are formed by a localized enlargement of the cylindricalconnectors.